Myocardial protection is an essential part of almost every cardiac surgery procedure. Many cardiac surgery procedures cannot be effectively performed on a beating heart because the motion of the heart muscle would interfere with the intricate surgical manipulations. Also, for procedures where the coronary arteries or one of the chambers of the heart must be opened, the blood pressure in the beating heart would cause excessive bleeding that would endanger the patient and obscure the surgical site.
For most cardiac surgery procedures, it is preferable to stop the heart from beating for a period of time so that the surgery can be performed while on cardiopulmonary bypass. It is important that the heart muscle or myocardium be protected and supported during the time that the heart is stopped so that it does not suffer cellular damage that would prevent the heart from working properly when it is started again. There are numerous aspects to the process of myocardial protection including: (1) reducing the oxygen demand of the heart muscle; (2) adequately oxygenating the heart muscle and maintaining the proper chemical balance so that cellular damage does not occur, and 3) introducing drugs and mechanical maneuvers that protect the heart.
There are two approaches currently used to reduce the oxygen demand of the heart muscle. The first is to stop the heart from beating by cardioplegic arrest. The second is to reduce the temperature of the heart muscle to reduce the oxygen demand, i.e. hypothermia. Currently preferred procedures combine these two approaches in a method known as cold cardioplegia (cardio=heart; plegia=paralysis). However, some surgeons use a warmer cardioplegia solution to arrest and protect the heart, but this warmer solution must be given more frequently or continuously throughout the surgery.
Typically, when open heart surgery is performed, the chest is opened using a median sternotomy to gain surgical access to the heart. This also allows access to the aorta for cross clamping, which is important for standard methods of administering cardioplegia because it effectively separates the heart circulation from that of the rest of the body. Before stopping the heart, the patient is prepared by placing an arterial cannula and a venous cannula which are connected to a cardiopulmonary bypass (CPB) system. The CPB system takes over the functions of the heart and the lungs of the patient by oxygenating and pumping the blood while the heart is stopped. Once the CPB system is connected and started, the ascending aorta can be cross clamped to isolate the coronary arteries from the rest of the systemic arterial circulation. Then, cardioplegic arrest is induced by injecting a prescribed quantity of cardioplegic solution into the aortic root proximal to the heart using a needle or cannula which pierces the wall of the ascending aorta proximal to the cross clamp. To stop the heart (cardioplegia), a solution is infused through a catheter placed in the proximal aortic root to be distributed to the heart via the coronary arteries selectively. After the induction of cardioplegic arrest, the surgeon may infuse solution intermittently (for example, every 20-30 minutes) to refresh the previous solution residing in the heart muscle, or the solution may be infused continuously (or nearly so) via a catheter placed in the coronary sinus. Whichever option is used, many surgeons deliver a final dose of cardioplegia solution through the aortic root catheter as a “terminal” cardioplegia before the cross-clamp is removed from the aorta, and systemic blood flow is restored to the heart (reperfused). After the surgery is completed, the needle puncture in the aorta must be repaired before the heart is restarted.
The construction and use of catheters and related medical devices is well known. As noted above, current technologies allow for the delivery of cardioplegia solutions to patients undergoing cardiac surgery. The cardioplegia solution, for example, a high potassium concentration solution, may be administered to the patient's heart in an antegrade direction through the patient's aorta, i.e., in the direction of normal patient blood flow. Conventional antegrade cardioplegia techniques require the use of a catheter lumen, multiple rummels and associated hemostats for securing the rummel sutures and for maintaining hemostasis around the insert of the catheter lumen and the aortic wall interface. The sheer number of “devices” typically required to accomplish the administration of the cardioplegia solution clutters the operative field. Of course, it is contemplated that solutions of other composition, i.e. non-depolarizing cardioplegia solutions with arresting agents other than potassium, may be infused through the cardioplegia catheter described herein.
What is needed, therefore, is a cardioplegia catheter system constructed and arranged to permit the controlled antegrade delivery of a cardioplegia solution into the aortic root of a patient that does not interfere with the visibility of the surgical field. Such a catheter system organizes and reduces the clutter in the operative field.